1. Field of the Invention
The present invention relates to an evaporated-fuel storage system in which a canister adapted to adsorb an evaporated fuel is connected to a fuel tank.
2. Description of the Related Art
Such evaporated-fuel storage systems are known from Japanese Patent Nos. 2808403 and 3158170, their corresponding U.S. Pat. No. 5,606,954, and Japanese Patent Application Laid-open No. 2002-2314 and its corresponding U.S. patent Publication No. US-2001-0054452-A1. In an automobile having such a conventional evaporated-fuel storage system, an upper space in a fuel tank is connected to a canister through an evaporated-fuel passage, and an opening connecting the evaporated-fuel passage to the fuel tank is opened and closed by a float valve. If a liquid surface in the fuel tank is raised by supplying a fuel from a filler tube through a fuel supply nozzle, an evaporated fuel forced out of the fuel tank into the evaporated-fuel passage is adsorbed by the canister, thereby suppressing dissipation of the evaporated fuel to the atmosphere. If the liquid surface in the fuel tank becomes a filled-up liquid surface, a float of the float valve is raised and seated in the opening, whereby the evaporated-fuel passage is closed to suppress the rising of the liquid surface in the fuel tank. Therefore, the liquid surface in the filler tube rises to operate an automatic stopping device for the fuel supply nozzle.
However, the conventional system suffers from the following problem: If a distance between an upper wall of the fuel tank in which a valve chamber is mounted and a filled-up liquid surface is large depending on the shape of the fuel tank, a distance between a valve seat formed at an upper end of the valve chamber and the float vertically movably accommodated in the valve chamber is large, resulting in an increase in the size of the entire float valve. In recent years, there is a synthetic resin fuel tank formed by blow-molding a special laminating material impermeable to fuel. However, if a valve chamber of a float valve made of a different material is fitted into and welded to an opening defined in a fuel tank, the valve chamber of the float valve permits a small amount of fuel permeation. Therefore, even if the fuel tank itself is made of a material impermeable to the fuel, there is a possibility that the fuel permeates through the valve chamber.